Sometime in the past few hub updates this command stopped working. Was this option removed from the hub? And/Or is there another way of accomplishing the same thing another way?
I thought that was addressed before then, but that could have been only for internal use by the hub. You could try a JSON body instead of URL parameters for your data, which I think worked even when this was temporarily broken for "official" usages before. (It's not really supported, so I'm still not saying it will, but that did work when the URL parameters didn't when this issue was first discovered...)
I wonder if this would be worth exposing over Maker API.
Based on this post, it doesn't look like you're sending a JSON body (or any) at all:
Based on that, it also looks like, unless you're using variables, you'd need to manually construct a JSON string to use for a "CUSTOM" body type (and eliminate the URL parameters — with some digging, that's what changed recently and no longer works, but JSON body still should and does to me externally to the hub with curl, so webCoRE on the hub should, too, if you find the right way to make it actually send what you want; I don't use webCoRE myself so won't be much help beyond that).